I've done a little research and it doesn't look like the Aqua Mail Plugin can do this, but Gmail (WebMail) has an auto-forwarding setting so you can create a message filter to forward only messages with attachments.
I've done a little research and it doesn't look like the Aqua Mail Plugin can do this, but Gmail (WebMail) has an auto-forwarding setting so you can create a message filter to forward only messages with attachments.